blurred:
1 not clear; without a clear outline or shape
2 difficult to remember clearly
3 difficult to distinguish, so that differences are not clear

I think that blurry is a derivative of the noun blur while blurred stems from the verb blur. But I wonder why there exists two forms. I tried to find other words where derivatives of both noun and verb with seemingly the same meaning exists to compare their meanings but I didn't find any. Those words which came to my mind have in my opinion a distinction. For instance, washed and washy.

Even though the quotes from the articles give the appearance that they are identical, is there any subtle distinction between blurry and blurred or are they interchangeable without changing any connotation?

2 Answers
2

Blurry can always be replaced by blurred (except in the word blurry-eyed), but not always vice versa. IMO, blurry, for the most part, fits all three meanings of blurred in the OALD excerpt, not just the first.

However, blurred has another use which blurry doesn't duplicate, and the dictionary doesn't bring out (probably because it's hard to do without examples). When blurred follows is, was, etc., (i.e. the picture was blurred), it can take a modifier or modifier phrase (e.g. the picture was blurred by the rain or the picture was badly blurred). Blurry cannot be used nearly as extensively in this way.

To go into nuances, even in the places where blurry and blurred are interchangeable, blurred suggests a previous state of non-blurriness and may suggest a perpetrator, whereas blurry only reports the state of the object and doesn't connote much more. The distinction is, however, only slightly observed in common usage.

have knocked out the comment because it no longer adds anything. The rest of your answer is fully-focussed and not even slightly blurry/blurred (or is that an artifact of my excellent sharp-pixelled monitor? :)
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FumbleFingersMar 19 '12 at 0:49

Having mused on OP's point about most adjective-derived-from-noun and past-participle-verb pairs having different meanings, I wonder if your final paragraph embodies any "generic" principle, where no other factors come into play. How does it play out with things like squashy/squashed, minty/minted, speckly/speckled, grainy/grained, etc.?
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FumbleFingersMar 19 '12 at 1:16

"The picture was hopelessly blurry" sounds fine to me. I think you're actually on very sticky ground trying to identify too many "ways" one or the other word can't be used - a lot of them will turn out to be highly-specific idiomatic usages.
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FumbleFingersMar 19 '12 at 14:46

Blurry is an adjective and does not have any particular implications as to why the image is indistinct, and will usually appear in the attributive and predicative positions:

The image is blurry.

The blurry image is useless.

Blurred is a participle and has additional usages available, and is more likely to occur in apposition. It has different shades of meaning too in that there is the more direct implication that it is the result of some (defective) blurring process as it derives from a verb. While an adjective can be used as a noun, this is slightly more common with a participle (which can in general be used as part of a compound verb, as an gerundive, or as a gerund). The point is not so much that 'blurry' couldn't substitute in all but the first of the examples below, but that we are talking about the result of a process (accidental in general, but deliberate in the case of the last one where 'blurry' would apply it was unintended). In the case of a photo of Doris Day, where photos of the actress were deliberately blurred to create a softer feel, we would not have 'blurry' as an option in examples 3 and 4 either.